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Avomine (UK), Histantil (CA), Phenergan (CA), PMS-Promethazine, Promethegan, Sominex (UK), Ziz (UK)
Pharmacologic class: Phenothiazine (nonselective)
Therapeutic class: Antihistamine, antiemetic, sedative-hypnotic
Pregnancy risk category C
FDA Box Warning
• Don't use promethazine in patients younger than age 2 due to potential for fatal respiratory depression. (Postmarketing cases of respiratory depression have been reported in these patients.)
• Use caution when administering to pediatric patients age 2 years and older. Preferably, use lowest effective dosage in these patients and avoid concurrent use of other drugs with respiratory depressant effects.
• Promethazine injection can cause severe chemical irritation and damage to tissue regardless of administration route. Irritation and damage can result from perivascular extravasation, unintentional intra-arterial injection, and intraneuronal or perineuronal infiltration.
• Adverse reactions to I.V. injection include burning, pain, thrombophlebitis, tissue necrosis, and gangrene. In some cases, surgical intervention, including fasciotomy, skin graft, or amputation, has been required.
• Because of risks of I.V. injection, preferred parenteral administration route is deep I.M. injection. Subcutaneous injection is contraindicated.
Blocks effects but not release of histamine and exerts strong alphaadrenergic effect. Also inhibits chemoreceptor trigger zone in medulla and alters dopamine effects by indirectly reducing reticular stimulation in CNS.
Injection: 25 mg/ml and 50 mg/ml in 1-ml ampules and 1- and 10-ml vials
Suppositories: 12.5 mg, 25 mg, 50 mg
Syrup: 6.25 mg/5 ml
Tablets: 12.5 mg, 25 mg, 50 mg
⊘Indications and dosages
➣ Type 1 hypersensitivity reaction
Adults: 25 mg P.O. or P.R. at bedtime or 12.5 mg P.O. before meals and at bedtime. Or 25 mg I.M. or I.V.; may repeat in 2 hours.
Children older than age 2: 25 mg P.O. or P.R. at bedtime or 6.25 to 12.5 mg P.O. t.i.d.
➣ Motion sickness
Adults: Initially, 25 mg P.O. or P.R. 30 to 60 minutes before traveling; may repeat 8 to 12 hours later if needed. On successive travel days, 25 mg P.O. or P.R. b.i.d. (on arising and before evening meal).
Children older than age 2: 12.5 to 25 mg P.O. or P.R. b.i.d.
Adults: 25 to 50 mg P.O., I.M., I.V., or P.R. at bedtime
Children older than age 2: 12.5 to 25 mg P.O. or P.R. at bedtime
➣ Adjunct to preoperative or postoperative analgesia
Adults: 25 to 50 mg P.O., P.R., I.M., or I.V. given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid
Children older than age 2: 0.5 mg/lb P.O., P.R., I.M., or I.V., given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid
Adults: 25 mg P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. Or 12.5 to 25 mg I.M. or I.V.; may repeat q 4 hours p.r.n.
Children older than age 2: 25 mg or 0.5 mg/lb P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. May give I.M. or I.V. as no more than half of adult dosage. Know that drug should not be given if cause of vomiting is unknown.
• Hypersensitivity to drug
• Previous idiosyncratic reaction to phenothiazines
• Intra-arterial and subcutaneous injection
• Children younger than age 2
Use cautiously in:
• cardiovascular or hepatic disease, seizures, bone marrow depression, narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal or bladder neck obstruction
• CNS depression caused by narcotics, barbiturates, general anesthesia, tranquilizers, or alcohol
• pregnant or breastfeeding patients.
• Don't give I.V. at concentrations greater than 25 mg/ml or faster than 25 mg/minute.
• Use light-resistant covering for I.V. drug.
☞ Inject I.M. deep into large muscle. Don't give by subcutaneous route.
CNS: confusion, disorientation, fatigue, marked drowsiness, sedation, dizziness, extrapyramidal reactions, insomnia, nervousness, neuroleptic malignant syndrome
CV: hypertension, hypotension, bradycardia, tachycardia
EENT: blurred vision, diplopia, tinnitus
GI: constipation, dry mouth
Hematologic: blood dyscrasias
Hepatic: cholestatic jaundice
Respiratory: respiratory depression
Skin: photosensitivity, rash
Other: hypersensitivity reaction
Drug-drug.Anticholinergics: additive anticholinergic effects
CNS depressants: additive CNS depression
Epinephrine: reversal of epinephrine's vasopressor effects
MAO inhibitors: increased extrapyramidal effects
Drug-diagnostic tests.Glucose: increased level
Granulocytes, platelets, white blood cells: decreased counts
Pregnancy test: false-positive or false-negative result
Skin tests using allergen extracts: false-negative results
Drug-herbs.Betel nut: increased risk of extrapyramidal reactions
Evening primrose oil: increased risk of seizures
Kava: increased risk of adverse drug effects
Drug-behaviors.Alcohol use: additive CNS depression
Sun exposure: increased risk of photosensitivity
☞ Monitor neurologic status. Stay alert for signs and symptoms of neuroleptic malignant syndrome (high fever, sweating, unstable blood pressure, stupor, muscle rigidity, and autonomic dysfunction).
• In long-term therapy, assess for other adverse CNS effects, including extrapyramidal reactions.
• Monitor CBC and liver function tests.
☞ Teach patient to recognize and immediately report signs and symptoms of hypersensitivity reaction or neuroleptic malignant syndrome.
• Tell patient about drug's other significant neurologic effects. Instruct him to contact prescriber if these occur.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, alertness, and motor skills.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.